[SOLVED] Enabled HTTP Reverse Proxy - Some Users Documents Go Missing

We enabled HTTP Reverse Proxy after upgrading to 6.0.4 from 5.0.18.

We've had several users report that their documents are missing.

Their folders still appear, but if they click on one of the document folders....the browser hangs as if it's waiting for something. After a few minutes it times out and a 504 error message appears in the main Zimbra window pane.